Metal buildings are commonly employed as an economical utilitarian structure. In most cases they are insulated against heat or cold through the use of fibrous insulation which in the case of roof insulation usually takes the form of fiber glass blankets supported on spaced purlins. The interior face of the insulation, which is exposed to view, is comprised of a vapor retarding material capable of functioning as a vapor barrier. Because the insulation can be seen it is important that it not present an unsightly appearance.
Metal building roof insulation previously available has included relatively low density fibrous material having little rigidity and relatively high density fibrous material having substantial rigidity. The low density material, which tends to sag unless supported on closely spaced centers, is often provided with a vapor retardant facing that extends beyond both longitudinal edges of the insulation for a distance of about 3". During installation these tabs are folded up and stapled to the folded tabs of the next adjacent row of insulation to provide a continuous vapor barrier. This arrangement is more labor intensive than desired and is less pleasing in appearance than desired.
Another previously available low density product incorporates only a single tab extending about 6" from one of the longitudinal edges of the insulation. When installed the edges of the insulation are butted and the tabs extend over the joints between adjacent insulation lengths. To provide an effective vapor barrier, however, it is necessary to glue the tabs to the underside of the adjacent lengths of insulation. Thus the installation time is slowed due to this operation.
A relatively high density metal building roof insulation product previously available also incorporated a facing having a single tab extending from one of the longitudinal edges of the insulation. The tab was reinforced by a portion of the facing sheet being folded upon itself or by a supplemental tape, and was thus able to remain in contact with the facing of the adjacent length of insulation without gluing or stapling. As a result, the installation of the material was faster than the installation of the low density product. The overall cost of the high density product was more than desired, however, because of the greater cost of the high density material.
In view of the drawbacks of the existing metal building insulation systems, it would be desirable to have available a low density metal building insulation which can be installed without having to glue or staple the facing tabs during installation. This would reduce the cost of the installation by allowing use of relatively inexpensive insulation without requiring the labor intensive installation practices of the prior art.